Uncle Rod's Astro Blog

A quiet little spot where Rod Mollise shares his adventures and misadventures...

Sunday, January 29, 2017

Issue #528: The Novice Files II: The Naming of Names

Last time in this series,
we discussed the features of the great sky globe, its lines and points, things
like the lines of right ascension and declination, celestial longitude and
latitude. This Sunday, we begin talking about destinations in the sky, the
objects those lines of declination and right ascension help us find.

Stars and
Constellations

The Naming of Stars is
an Important Matter

Do you remember T.S. Eliot’s Old Possum’s Book of Practical Cats? No? Surely, though, you’ve heard
of the famous musical based on it, Cats?
Anyhow, Eliot informed us that every cat
has three names. The same is true of stars. Every star you can see in the
sky—and many thousands and thousands beyond those you can see with your naked
eye—has (at least) three names.

Even if you’re the newest of novices, you probably know at
least a few star proper names. You’ve probably heard “Polaris” (a.k.a. The
North Star), possibly “Sirius” (the brightest star in the sky, “The Dog Star”),
and very likely “Betelgeuse” (“Beetlejuice, Beetlejuice, Beetlejuice!”). You
may also assume that’s how astronomers identify stars, by their proper names.
While astronomers, amateur and professional, do tend to refer to a handful of
brighter stars by their names, that’s about it.

Why is that? First of all, only a relatively few stars,
maybe a couple of hundred out of the four or five thousand visible to the naked
eye, have proper names. Also, most of the star names in common usage are of
Arabic origin and are difficult for non-Arabic speakers to pronounce and
remember. Sure, Betelgeuse is easy enough, but then you have Zubenelgenubi, Al Minliar al Asad, and Fum al Samakah. There’s got to be a better way.

There was, beginning with an alternative means of identifying stars
devised by German astronomer Johannes Bayer in 1600. He hit on a star
nomenclature system that was simple and elegant and is still widely used today.
Bayer dispensed with proper names and instead
christened stars with lowercase Greek letters. Often, but not always, he
designated the brightest star in a constellation as “alpha,” the second
brightest as “beta,” and so on. Sirius in the constellation Canis Major, for
example, is identified with the letter alpha and the Latin genitive of its
constellation name, “Alpha Canis Majoris.” Simple, neat, elegant.

Unfortunately, there are serious problems with the Bayer
Letter system. First, Johannes didn’t always stick to the “brightest star is
alpha” rule. Sometimes, the placement of a star in a constellation was more
important to him than its brightness. For example, Adhara in Canis Major is the
second brightest star in its constellation, but because it is far to the south,
he gave it the letter epsilon rather than beta. The most fatal problem for
Bayer letters, however? There are only 24 Greek letters, so even a small
constellation exhausts the alphabet in a hurry.

What’s the one thing you can’t run out of? Arabic numerals.
That’s what occurred to 18th Century French astronomer Joseph
Lalande as he was working with the star catalog (list) of British Astronomer
Royal, John Flamsteed. The other idea Lalande had was to not worry about stellar brightness. In an age long before the development of
photometers, it was often hard to tell which stars were brighter than others,
especially considering that some stars, like Algol in Perseus, are
variable—their brightness changes.

What Lalande did instead was to give each star in a
constellation a number based on its right ascension, its celestial longitude.
The westernmost star in Canis Major would be “1 Canis Majoris,” and the star
just to the east of it would be “2 Canis Majoris,” and so on. Is Lalande’s
system, which came to be called “Flamsteed Numbers” for the catalog he applied
it to, perfect? No. Due to the effects of precession, the slow wobble of the
Earth’s axis, which affects the coordinate system over time, some of Lalande’s
numbers are now out of order. That is not a big deal, though, and today
Flamsteed numbers are probably still the most oft-used identifiers of stars.

Proper names, Bayer Letters, and Flamsteed
Numbers are the only designations stars possess, however. There have been dozens of star
catalogs compiled in the last four centuries up to and including the Hubble
Guide Star Catalog, which contains millions of entries, and even beyond that to
catalogs with many millions of entries. So, many stars actually have
considerably more than three names.

Constellations

If you knew “Betelgeuse,” “Sirius,” and “Polaris,” you
probably also know a few star patterns, “constellations,” or parts of them at
least. Likely the Big Dipper (part of the larger constellation Ursa Major), and
perhaps Orion the Hunter, who is prominent in the sky right now. And you
probably know these constellations as often distinctive “stick figures.” The bright stars of part of Ursa Major seem to form
a dipper or plough, Orion is the outline of a man complete with a belt and
sword.

These constellation stick figures are useful, and even
professionals employ them to orient themselves in the sky on the infrequent
occasions when they have reason to look at the sky with their own eyes. Certainly,
amateur astronomers use them frequently. They are an easy way to find
objects—stars, planets, deep sky objects. The constellation stick figure
outlines are informal however.

There are no official constellation stick figures. Designs
for the constellation outlines range from the simple and elegant, as those in Sky & Telescope’s monthly star
chart, to the strange and torturous ones drawn by children’s author H.A. Rey in
his book, The Stars, a New Way to See
Them in an effort to make the figures look more like the things they are
supposed to represent (the usual stick figure of Sagittarius looks like a
teapot, not an archer). There are official
constellations, however.

A “constellation” as thought of by professional astronomers
and most amateur astronomers is a different thing. It is not a stick figure. As
shown above with Orion, a constellation in this sense is an area of the sky. Everything within the blue, dashed border is in
the constellation of Orion whether it is part of his stick figure or not. These
sorts of constellations are analogous to the counties on a state map. There is
a combined total of 88 constellations in the sky’s Northern and Southern
Celestial Hemispheres, and their boundaries were made official by the
International Astronomical Union, the body that handles the naming of objects
in astronomy among other things, in 1922.

Deep Sky
Objects

What’s a “deep sky object” (DSO)? We’ll save the minutiae of
star clusters, galaxies, and nebulae for a future installment. Today, we’ll just talk generalities. Deep sky objects are those things other than single stars that lie beyond the Solar System: star clusters, galaxies, and nebulae. Some observers consider double stars to be DSOs, but most don't.

The basic amateur astronomer “life list,” the Messier catalog, composed by French
Astronomer Charles Messier in 1781, and was, initially a listing of odd fuzzy
things Messier saw with his small telescope (often a 4-inch refractor). The
Messier is the place to start when you are beginning your exploration of the
Universe outside our Solar System. Initially, Messier’s idea was to catalog
fuzzy objects that could potentially masquerade as comets, confusing his fellow
comet hunters.

The objects in Chuck’s list are commonly identified as M-1,
M-2, etc. All are visible from the northern hemisphere, natch, with even the
southernmost objects doable from mid-northern latitudes.

While the original goal of the M-list may have been to aid
comet hunters, Messier soon went beyond that, including objects, like M45,
the Pleiades star cluster, that surely no one could have mistaken for a comet.
The M-list not only contains objects that Messier and his friends and
colleagues saw, but those from other sources, including some, like the Orion
Nebula (M42), that had been known for a long time. While Messier’s original
list stops at M103, seven more have been added over the years by various people,
with the “Messier” now widely considered to contain 110 objects.

The next person to compose a major deep sky catalog was the
famous English amateur astronomer William Herschel in the latter part of the 18th
Century. He and his sister Caroline cataloged a whopping 2500 faint fuzzies.
While the Herschel Catalog is
famous, it’s no longer in use. It was absorbed into the even larger NGC catalog
developed by Herschel’s son, John and John Louis Emil Dreyer in the 19th
Century.

While the most popular list of deep sky objects with
amateurs after the Messier is the Herschel 400 list, a subset of Herschel’s
catalog containing the 400 best objects for smaller telescopes, the DSOs in it
are identified by their modern NGC numbers, not their old Herschel
designations.

The New General
Catalogue of Nebulae and Clusters of Stars (abbreviated “NGC”) is the bread
and butter deep sky list for astronomers amateur and professional. The basic
catalog contains 7840 DSOs total for the Northern and Southern Hemispheres. An addition to the NGC, the two-part Index Catalog (IC) published by Dreyer in the
late 1800s, brings the final NGC object tally to 13,226 DSOs. NGC objects are identified with "NGC" or "IC" and a four digit number following a space, "NGC 7331," for example. While technically considered part of the NGC the IC catalogs' numbers begin with IC 1.

While many NGC objects are, yes, dimmer than Messiers, and
new amateurs can be a bit skittish about diving into the bigger list, not all its
objects are tougher than the Ms. There are plenty of showpieces Charles Messier
missed. For example, the spectacular galaxy NGC 253 does not appear in the
M-list. All the Messier objects also have NGC numbers, by the way. M31, the
Andromeda galaxy, for example, is also NGC 224. How about the IC? Most of
them are indeed tough. Oh, there are some easy IC open clusters, but most of
these catalogs’ DSOs are faint and difficult “photographic” subjects.

There are plenty of other catalogs besides the Messier and
NGC. Most are specialized like the PK catalog of planetary nebulae or the
Collinder catalog of open star clusters. Some, like those two, are in common
use by amateurs. Others like the PGC and UGC catalogs, which contain millions
of faint galaxies, are only used by those of us with the largest telescopes or
most sensitive cameras.

And…I think we’ll stop right here. The next “lesson” will
concern star charts, and will, like the first installment, be a lot for Joe and
Jane Newbie to bite off and chew in one sitting. When will that come? As
before, it depends on the weather. I currently have a telescope set up in the
backyard, but it is sitting under layers and layers of thick, nasty clouds.

Sunday, January 22, 2017

Issue #527: The New Stellarium

I don’t claim to be some kind of software guru, but I have
been using astronomy software since computers first came to our avocation. Most of you know that, and I am often asked which
software I use. Those asking are sometimes disappointed when I say, “Whatever
is cheap and simple” rather than “The latest version of TheSky X Professional (or
Maxim DL).” In part, that’s because I am
cheap. And it’s also in part because the things I do in astronomy today are
simple enough that they could probably be accomplished with a 20-year-old copy
of Megastar.

Just because I don’t spend a lot/any money on the software
than runs on my PCs (no Mac here despite my not infrequent threats to go Apple)
doesn’t mean my astronomy programs aren’t capable of doing far more than I do
with them. We are in a golden age of incredibly capable astronomy freeware with
softs like Cartes du Ciel, Deep Sky Stacker, Sharpcap, Astrotortilla,
Auto Stakkert, ASCOM, Registax, and,
the subject of today’s article, Stellarium.

Yes, there are tons of excellent planetarium programs,
freeware and payware planetarium programs, beyond the above mentioned Cartes (a
long time favorite of mine and a wonderful piece of software) and TheSky X, but
what I use more than anything else today is Stellarium. Why? It’s simple and
it’s pretty and that is exactly what I appreciate at the moment. It also does
everything I need, and could do far more than I ask it to. If you’re interested
in the basics of Stellarium, including how to install and configure it, see this article(from over five years ago, hard as that is for me to believe). Today, we’ll mostly be looking at what’s
new in the latest release, Stellarium 15.1.1.

To make the above-linked long story short, Stellarium, in
addition to being free, is a relatively quick download, and while, like any
astronomy software, it needs to be configured, it’s not that tough. For the
most part, there are no submenus of submenus of submenus. You get some fairly
clear choices in a few (multi-tabbed, admittedly) windows, “Location,” “Sky and
Viewing Options,” and “Configuration.” It’s all easy to do and it’s fairly
obvious what you should do without
even looking at help pages.

Without (top) and with (bottom) DSS (click to enlarge)...

Even setting up a connection to a telescope is not that bad.
It’s duck soup if you can use the program’s built in telescope drivers
(Celestron, Meade, Losmandy, SkyWatcher, Argo Navis). If you have a non-compatible
telescope, you’ll have to use an add-on helper program, StellariumScope to give
the program access to the multitudinous ASCOM telescope drivers, but even doing
that is fairly simple.

How much computing horsepower does it take to run
Stellarium? For the current version you’ll want a reasonably fast processor, but
a 2.4 gig one like those in even the cheapest boxes from BestBuy is more than
sufficient. Most important is a video card that supports the Open GL graphics system. You’ll also want Windows 7 and up, OSX and up, or a reasonably current
flavor of Linux/Unix as your operating system. You can download older versions of Stellarium to
accommodate older OSes and video cards, but you really don’t want to.

What is the first thing you will notice the first time you
boot up Stellarium? Just how beautiful it is. This software is used in
conjunction with projectors in planetariums, and it’s easy to see why. Its sky
is as realistic as those in the most expensive apps. Weather, fog, passing
satellites (actual satellites), sporadic meteors, beautiful horizon scenery,
and a luscious looking sky with a superb rendition of the Milky Way are all
there. You can download plenty of additional stars, and the program contains
thousands and thousands and thousands of deep sky objects. Movement around the sky, dragging
it with a mouse, is wonderfully responsive.

But those of you who’ve, like me, been using the program for
a while know all that. What you want to know is, “Why should I go to the
trouble of downloading the new one and going through that configurating again?

That first thing, DSS, is the money here. Being able to
download and overlay Digitized Sky Survey images on Stellarium is a wonderful
tool. Sure, you need an Internet connection, but it’s getting to the point
where many star parties provide that. Not only are the charts prettier with DSS,
they are more detailed. Compare the program’s normal display of M33, the
Triangulum Galaxy, to one showing the DSS image of M33 (above). What’s really cool
about this feature? Plenty of planetarium programs allow you to superimpose DSS
images over their charts, but most require you to be zoomed in tight. Not
Stellarium. The image at the beginning of this post is 30-degrees of Cygnus with DSS “on.”

Astrocalc...

While the program’s developers warn the Digitized Sky
Survey feature is still somewhat experimental, it worked flawlessly for me.
Occasionally, when using wide fields of view, there were a few “stitching”
artifacts, but these didn’t bother me or cause problems. DSS is reason enough
to upgrade to the new Stellarium. The current release is 15.1.1, btw, because
the initial 15.1 build had problems with missing dlls, which prevented you from
downloading the additional star catalogs offered for the program.

“Astrocalc” is Stellarium’s text-based ephemeris module. You
can now overlay it on the screen with a push of the F10 button. In addition to
ephemerides, this tabbed window will give positions for comets (clicking on a
comet in the list will center it on the chart), find conjunctions, and display
a graph showing altitude versus time for the selected object. That last is
similar to the observability graphs offered in several other programs, and it
is a very popular and useful tool for me.

The other additions, like a new “sky culture” (constellation
system), are more minor, but still welcome, and undoubtedly useful to some of
the program’s large base of users. As above, Stellarium is used by more than a few planetariums
and science museums. More important to most of us, I suppose, are the updates
and expansions to the program’s deep sky and star catalogs.

There’s always that ever-popular question among deep sky
hounds, “How many DSOs does it got?” I don’t know that there’s a numerical
total anywhere on the Stellarium website, but the DSO catalog has undoubtedly
grown with the last couple of releases. For example, zooming in on a field in
Coma revealed plenty of magnitude 16 PGC galaxies. I am more interested in
imaging and observing the bright and spectacular galaxies, clusters, and
nebulae these days (I used to chase
Arps, PGCs, and UGCs), but if I were currently interested in the dimmest of the
dim, I’d still be just fine with Stellarium.

What’s the experience of using the program like for those
who haven’t tried it yet? Most people tend to think of this as a very visual, GUI oriented program, and it
can be that. Grab the sky and drag it around, use the roller ball on your mouse to
zoom. It’s a silky smooth and, yeah, visual
experience. Strangely, however, one of Stellarium’s major strengths hearkens
back to the earliest days of computing. What it’s very strong with is hot keys.

Yes, it’s cools to mouse over to the left side of the screen
(which makes one of the program’s tool-icon-menus appear), click that pretty “find”
icon, and locate what you want with the aid of the window that comes up. Cool,
yeah, but somewhat annoying out on a dark observing field. Much easier/simpler is pressing F3, which summons that same window without mousing around and clicking.
Much of what you need to do with the program can be done quickly with F keys
and key combos. , for example, takes you do the eastern horizon
post-haste.

It's just so pretty!

The ability to do things quickly with hot-key combos doesn’t
end with the things built into the program by the developer. Stellarium
includes a powerful scripting system that will allow you to compose scripts to
do things with a few key presses, things as simple as pointing at a
certain object, or as complex as taking you on a tour of the best NGC objects.

How do I use Stellarium? Basically, in three ways. First, I
use it to give me quick “What’s up?” looks at the sky. You know, “What’s high
in the east right now?” After Windows changed enough that that DOS oldie but
goodie, Skyglobe, would no longer run, I cast about for a program that was quick
to load and would let me get to my chosen horizon in a hurry. Initially, I used
the free soft I got with my Edge800/VX telescope four years ago, the lowest level
of Bisque’s TheSky X, the First Light Edition. That’s a nice but very limited
program (natch), so I was pleased to be able to ditch it for the recent
releases of Stellarium, which load quickly on my modern PCs, and which offer
those quick hot-keys to allow me to get to anything and anywhere.

Secondly, I use Stellarium when writing observing articles,
whether for this blog or for Sky &
Telescope. The program has an excellent measuring tool that allows me to
easily determine that NGC Umptysquat is 3 degrees northwest of M Whatsit.

Finally, I use Stellarium in the field with my telescope.
While there are built-in drivers for all my mounts, I generally use the
SteallariumScope program and ASCOM drivers, since ASCOM gives me some things
the built-in drivers don’t, like a little onscreen hand control. That allows me
to center objects I am imaging without messing with the real HC (and prevents
my editor from complaining about my poorly centered/composed astrophotos). Going to objects with Stellarium is a breeze,
by the way. Select an object, hold down the CTRL key and press “1.” That’s all.
No icons to hunt or menus to navigate.

In the field, I often use Stellarium alongside a planner/logger—SkyTools,
Deep Sky Planner, or Deepsky. While you can’t interface Stellarium with Deep
Sky Planner as you can some other planetarium programs, I don’t find that a huge
problem. I locate an object in DSP’s database, switch to Stellarium, hit the F3
key, and type in the object identifier, Not a big deal. And then I just do my
thing with Stellarium and my telescope. I have never had any problems with or program
crashes in the field. Yes, computers can be cantankerous, but Stellarium is exemplary for its good behavior.

And there you have it. If you are a Stellarium user, you’ll
want to upgrade ASAP in order to get the DSS feature. Not a Stellarium user? As
I said earlier, there are many great free planetariums these days, like Cartes
and Hallo Northern Sky, but since there’s no money involved, why not give
Stellarium a try; you just might like its way of doing things. You are firmly
in the TheSky X or Starry Night camp? Again, it don’t cost nuthin’ so why not
try Stellarium? There’s a lot to be said for “simpler.” Me? I’m allergic to
menus within menus within menus, and that’s one of the reasons I’ll be rolling
with Stellarium for a while, I think.

Saturday, January 14, 2017

Issue #526: The Novice Files Part I

It’s 1965 and I’ve just gotten my first real telescope, a
3-inch Tasco Newtonian (a pawn shop refugee). I really don’t know what the heck
to do with it other than look at the Moon—which is wonderful, of course.
Shortly, though, my first issue of Sky
& Telescope arrives. Surely it will clue me in to everything I need to know about this amateur astronomy business. Alas, after looking through it I
wind up more puzzled than I was before.

Sure, there was ample amateur astronomy in the magazine (if
not as much as today) following the pro/science articles up front. But the
writers seemed to think I already knew enough about astronomy to understand them.
Heck, even the advertisements were indecipherable due to the jargon. I was
getting nowhere in a hurry.

What was a “clock drive”? When the author of an article said
an object in the telescope was “30’ northwest” of another, did that mean the
object was 30-feet from the other
one? How could you tell what was north or south or east or west in the eyepiece
anyway? What was a “Meridian” or an “Ecliptic”? What did “R.A.” and “Declination”
mean? What was “figuring” a mirror? Why did it have to be “parabolic”? What was
a “prime focus”? What in God’s name was a “drive corrector”?

My confusion didn’t last too long. Between the mutual support
and advice me and my buddies gave each other in our little proto-astronomy
club, the Backyard Astronomy Society,
and the wisdom dispensed by some of Patrick Moore’s books, I finally got off
square one. It wasn’t easy in the beginning, though, and I sure wished somebody
had explained all those puzzling things somewhere clearly, simply, and in one
place.

Today, with the Internet, things are easier, much easier, but
it would still be nice to have explanations of the basic concepts and terms of
practical astronomy in one spot. Certainly astronomy is every bit as foreign
and confusing for beginners now as it was back then. There’s a reason for that.
At the beginning of the last century, U.S. secondary science educators decided
to deemphasize geology and astronomy in favor of biology and chemistry. Most
students get very little on astronomy after the occasional middle school “space
science” unit, and its ideas and language are a mystery to most.

The sky globe...

So? In hopes of making that learning curve a little
less steep, here are some brief solutions to the head-scratching puzzles
you, Joe and Jane Newbie, are running into on the Internet and in the astronomy
magazines. There won’t be room to give
you everything you need to know in one go, so we’ll do a part II (maybe
even a part III and IV) in fairly short order.

The Sky
Globe

Many beginners have an awfully hard time wrapping their heads
around the way the sky works. All
those imaginary lines and stuff, and it’s always in motion! There is an easy
way to understand it, however. What did the Ancient Greeks think the sky was?
They believed it was a great crystalline globe surrounding the earth. The stars
were points of eternal fire, or maybe they were holes in the sky globe allowing
the eternal fire beyond to shine through. Of course, today we know that is
nonsense. The sky isn’t a glass globe. If, however, you can suspend your
disbelief for a while, thinking of the sky as a globe makes it easy to
understand how it works.

So, we have this great crystal
rotating about the earth once every 23 hours 56 minutes and 4 seconds (a “sidereal
day,” see below). Yes, I know it’s really the Earth that’s rotating, but
remember what I said about "suspension of disbelief"? To our eyes, it’s the sky
that is turning.

Lines and
Points

Celestial Poles

If you have a basic knowledge of Earthly geography, the globe of the Earth, understanding the lines and points of the sky is easy. Let’s begin with the
celestial poles, the analog of the Earth’s poles. Extend the axis of the earth
north and into the sky. The point where the Earth’s axis penetrates the sky
globe is the North Celestial Pole (NCP). Extend the axis south into the sky
globe and you have the South Celestial Pole (SCP). The sky globe appears to be
rotating on this axis, which extends from the North Celestial Pole, through the
Earth, and into the South Celestial Pole.

Where are the poles in the sky? They are found at an
elevation (north or south) equivalent to your latitude value. Down here, I am
at 30-degrees north latitude, so I find the NCP 30-degrees above the northern
horizon, conveniently marked by the bright 2nd magnitude star,
Polaris (which is actually about ¾ of a degree from the true NCP).

Celestial
Equator

Do the above with Earth’s equator, extend it into the sky as
a flat plane, and you have the Celestial Equator. The Celestial Equator is the
imaginary line that divides the sky globe into a Northern Celestial Hemisphere
and a South Celestial Hemisphere, just as the earthly equator separates the
globe into northern and southern hemispheres.

Latitude
(Declination)

Look at the globe of the Earth. How do you find your position
north and south of the equator? Simple: there are imaginary lines of latitude. We have the same thing on the
sky globe, lines of latitude. They perform exactly the same job; they allow you
to find your position north or south of the Celestial
Equator.

As on earth, latitude is measured in degrees, minutes, and
seconds beginning at the equator, which is 0-degrees. For some odd reason some beginners
tend to think the equator should be 90-degrees, but 90 degrees north or south
of the Celestial (or terrestrial) equator brings you to the poles. The equator
in the sky or on earth is 0-degrees. Latitude is measured in (angular) degrees,
minutes and seconds.

Conventions for stating a latitude value? Degrees are
indicated with a degree symbol, a single quote (‘) is minutes, and a double
quote (“) is seconds, just like in your high school geometry or trigonometry
courses. A minute is a distance equal to 1/60th of
a degree, and a second is a distance that’s 1/60th of a minute. North
thirty degrees, thirty minutes, and thirty seconds is written as 30°30’30”. If you don’t have a degree
symbol in your font, a lowercase “d” will do.
If the latitude in question is a south latitude, a latitude south of the
Celestial Equator, a minus (-) sign is placed in front of the value. You can
put a plus (+) sign before a latitude to indicate “north,” but the lack of a
minus sign is taken to mean it’s a north latitude.

There is one difference between latitude on the Earth and latitude
in the sky: in the sky this north-south
measurement is called “declination”
(abbreviated “dec”) but that is the only difference. “Declination” might sound
forbiddingly technical to you, but it’s not; it just means “latitude on the sky
globe.”

Longitude (Right
Ascension)

Just as the sky globe has lines of latitude, declination,
that allow us to locate points north and south of the Celestial Equator, there
are also lines of longitude that enable us to find positions east and west.
Just as on Earth, the combination of heavenly latitude and longitude allows us
to find anything we want—stars, planets, and deep sky objects.

Celestial longitude is actually simpler than earthly
longitude. On earth, longitude is in east and west values. Just as latitude is
stated in relation to distances north and south of the equator, longitude on
Earth is stated in terms of how far east or west (+/-) you are from the Prime
Meridian (the zero line of longitude, which runs through Greenwich England).
Longitude in the sky is simpler in that it begins at the sky’s Prime Meridian
and runs east, increasing in value, until it comes back around. There is no east/west in celestial longitude.

When talking latitude, it’s easy to see where you measure
from. On Earth or in the sky, it’s obvious you begin at the equator. But for
longitude, you must choose a
starting place. There’s no really obvious place to place the 0 line. On Earth,
that line runs through Greenwich, England. Why? Britain was the world’s preeminent
naval power when navigation was being sussed, and led the world in the quest to figure out how to determine
longitude at sea (not so easy). But where to put the 0 line of longitude in the
sky?

Ecliptic

Before talking about the sky’s Prime Meridian, you need to
understand another line, the Ecliptic.
The Ecliptic Is the Plane of Earth’s Orbit. The major planets are in orbits
that are almost in the same plane as the Earth's. As such, they always appear
close to the ecliptic. In terms of what you see in the sky with your eyes, the
Ecliptic is the apparent path of the Sun
through the sky. This path does not remain in the same positon throughout
the year, however.

The Vernal Equinox

You may have noticed that the Sun’s path is farther north in
the (Northern Hemisphere) in summer, and farther south in the (Northern Hemisphere)
winter. The path of the sun moves north and south over the course of the year.
When the path is farthest north, it is summer in the Northern Hemisphere.
Farthest south and it is winter (reverse that if you live in the Southern
Hemisphere). The Sun’s moving path across the sky and the change of the seasons
are due to the tilt of the earth’s axis. That’s why we have seasons. It’s not
because, as some astronomy newbies (and other people) imagine, the Sun is
closer in the summer thanks to the Earth’s elliptical orbit—the reverse is
actually true in the Northern Hemisphere.

Vernal
Equinox

Back to celestial longitude. The chosen point, the place the 0
line of longitude, the prime meridian in the sky, runs through is the Vernal
Equinox. The Vernal (spring) Equinox is the point where the ecliptic intersects
the celestial equator. As winter ends, the path of the ecliptic moves north,
and eventually runs into the Celestial Equator. When the path of the Sun
reaches this point, when the Sun hits the Celestial Equator, it is spring. The
zero hour line of celestial longitude passes through this point. The Vernal Equinox point is also known as "the First Point of Aries" (the Vernal Equinox no longer lies in Aries, but don't worry about that right now).

Right
Ascension

Since, as above, there is no east/west value for celestial
longitude, that makes it simpler to work with. Two things make it more
complicated, or at least complicated sounding
to novices, however. The first is its name. Just as celestial latitude is not
called “latitude,” celestial longitude is not called longitude. It is “right
ascension” (abbreviated R.A.) That’s scary sounding, but just remember right
ascension = longitude. What hangs most newbies up is not celestial longitude’s
name, but the way it is measured.

Rather than being given in degrees, minutes, and seconds as
latitude is, right ascension is measured in hours,minutes, and seconds. What you have to understand is that these hours, minutes
and seconds do not really describe time;
they describe distance. One hour of
right ascension is 15 angular degrees. 1-minute is 1/60th of that
and 1-second is 1/60th of that.

The seasons...

Why “hours” instead of degrees? Since the sky is always in
motion, it makes a certain amount of sense. Let’s say you go out one evening
and look to the eastern horizon. You notice the bright red giant star,
Aldebaran. “Pretty!” you think. But you want to watch a rerun of your favorite
program, Jersey Shore, on TV. You hop
inside and enjoy Snookie’s antics. Afterwards, you wander back outside and
immediately notice that in one hour Aldebaran has risen 15-degrees in the sky. It has moved a distance equal to one
hour of right ascension (multiply 15 times 24-hours and you
will come out with 360-degrees).

If you just understand that R.A. = distance, 1h = 15-degrees,
you will do OK. The convention for stating R.A. is a lowercase “h” denoting
hours, an “m” for minutes, and an “s” for seconds as in: 19h17m00s.

Zenith

The Zenith is the point in the sky that is directly over your
head. It never moves.

Nadir

The Nadir is like the Zenith, but is the point that is
always directly beneath your feet. Like the Zenith, it never moves.

Local
Meridian

Yet another imaginary line you need to know is the Local
Meridian. It is the line that runs from the North Celestial Pole to the Zenith,
through the South Celestial Pole, through the Nadir, and back around. It never
moves. As time passes, celestial objects—the Sun, the Moon, planets, stars,
deep sky objects, everything—hit and cross this line. When an object touches
the Local Meridian, it is said to be “culminating” or “transiting.”

When an object culminates is an important thing for a sky
watcher to know. When a star, for example, is on the Local Meridian, it is as high as it ever will get in your
sky. If it’s located very far north or south in declination, that might not
be very high, but it is still as high as the star will get. And that’s the best
time to observe it, when it is as far from the thick, dirty air on the horizon
as possible.

Solar day...

Local
Sidereal Time (LST)

How do you know when an object will transit the Local
Meridian? You check the local sidereal time. When a line of right ascension is
straight overhead on the Local Meridian, that is the current LST. Say the
11-hour line of right ascension is on the Meridian. That means the LST is
11:00. Any object with a right ascension, a celestial longitude, of 11h is
culminating.

How can you find out what the LST is? Most astronomy program, especially planetarium programs, will give LST. Some, like Stellarium, will display this
value as “Mean Sidereal Time” and/or “Apparent Sidereal Time,” but for our purposes that's the same as LST. Right now, it’s
19:17 and globular cluster M56, which has a right ascension of 19h17m, is on
the Local Meridian and high in the sky. Typically planetarium program, including Stellarium
and Cartes du Ciel, display LST in the information window that comes up when
you select an object.

Sidereal Day
and Solar Day

Yes, yes, I know back in first grade your teacher, kindly
Miss Franklin, told you a day is 24-hours long. But that’s not exactly true.
Not always. The actual time it takes the Earth to rotate once on its axis (as
measured by the time it takes a star to make two transits of the Local Meridian)
is 23 hours, 56 minutes, and four seconds.

So what’s with the “24-hours”? That’s a Solar day, the time it takes for the Sun to transit the Meridian twice. Why the difference? The Sun is
close compared to the stars, and the fact that the Earth is moving along in its
orbit in addition to rotating, means a bit of parallax error comes into play.
As you can see in the picture, when the Earth has rotated once on its axis,
it’s moved along in its orbit (greatly exaggerated here) as well, and, so, has to turn
a little more on its axis to put the sun back overhead. That extra time is the
nearly four minute difference in the two varieties of day.

Measuring Distances
in the Sky

All this degrees and minutes stuff is well and good, but how
do you judge distances in the sky? Luckily, nature has provided you with a
convenient measuring tool. Your outstretched fist covers about 10-degrees from
thumb to pinky. Your index finger is approximately 30’ across. “But Rod,” you
might say, “I have small hands.” Nevertheless, this should still work. Most
people with small hands have correspondingly short arms, and your outstretched
fist will still span 10-degrees.

Whew! That was a lot. Nearly too much for one sitting, so we
will stop here. Go over these concepts until you are clear on them; these are
things every astronomer needs to know. Even in this day of do-everything
computerized telescopes, I believe it is still vital—for understanding and enjoyment—that
you know how the great sky globe works.

Next time? I am not sure. I’d say that if the weather
continues to be as lousy as it is right now, we might go on to Part II of the
novice files. Or I may talk about the new Stellarium. Or something else may
come into my mind (such as it is). We shall see.

Sunday, January 08, 2017

Issue #525: This is the End, My Friends

And, so, we
find ourselves at the end of the Messier road. Don’t feel sad, though. While
we’ve caught ‘em all here, if you haven’t seen them all with your own eyes and
your own telescope, you have a huge adventure in store and I envy you. Even if
you have observed the entire list,
you, like me, will likely never tire of these beauties. Why not give the Ms
another go? This is a great time to begin that; the fall wonders are still
around, the winter spectacles will soon be riding high, and before you know it
the multitudinous Messiers of spring will be on parade.

This
actually isn’t the end of Messiers in the blog. Since I am mostly focused on
bright and spectacular deep sky objects these days, you can expect another
Messier series shortly. I won’t keep you in suspense about it, either. The new articles will involve me viewing the
list as John Mallas did for his and Evered Kreimer’s famous book, The Messier Album, with a 4-inch refractor. When will the series begin? That
depends on a number of factors, not the least of which is the weather.

What will I
see with my Celestron C102 compared to what Mallas saw with his 4-inch Unitron?
Will my drawings even remotely resemble his sometimes-eccentric/fanciful
looking ones? I actually did some observing along these lines some years ago,
writing more than a few blog entries about the experience. At the time,
however, I didn’t have a 4-inch refractor—I used a 5-inch MCT instead—so I
think it will be fun to revisit the Messier Album with a scope more similar to
what John used. I also plan to be more systematic this time, drawing every
object John drew. If you want to follow along, I urge you to get this fine book. It’s out of print but easily
available.

M106

M106

Messier 106,
a bright (as galaxies go) Sb spiral galaxy in Canes Venatici, is one of the
least visited and least appreciated M-galaxies. Why? I am not sure. While it’s
large at 18’36” x 7’12”, it’s also bright at magnitude 8.41, and its
intermediate inclination means its light is not badly spread out. Certainly,
it’s a nice sight in the suburbs with 10-inch range scopes, and is visible in
smaller instruments.

Part of the
problem may be that while not exactly tough to find, M106 is kinda out in the
middle of nowhere, lying about halfway along a line drawn between Chara, Beta
Canum Venaticorum, and Phecda, Gamma Ursae Majoris (a bowl star in the dipper
asterism). Thanks to the galaxy’s relative prominence, it shouldn’t be tough to
run to ground manually, however. If you need further guidance, it is 1-degree
40’ southeast of magnitude 5.25 3 Canum Venaticorum.

What will
pop into your mind when you arrive on the field of M106? “Whoa! Bigger than I
thought.” You may see as much as 10 – 12’ of galaxy, and it will be obvious
that it’s strongly elongated. Even on poor nights you may also make out a small
nucleus, albeit with some difficulty, as I did one hazy backyard evening with my
C11:

M106 is surprisingly attractive despite haze. Easily visible
in the TeleVue Panoptic 22mm with direct vision. Occasionally, I think I see
hints of a nucleus, but not often. obviously elongated North/South.

On good
nights from a darker site, a 10-inch class scope should reveal at least trace
of dark details.

M107

There are
globulars and then there are globulars. Ophiuchus has plenty, but not all are
like its two gems, M10 and M12. M107 is not a bad glob, mind you, just not an
outstanding one. Think “M53.” It’s resolvable from the suburbs, but you will
likely need 10-inches of aperture to do it, and upping the power is a must.

M107

One good
thing about M107 is that it is trivial to find, lying only 2-degrees 43’ southeast
of a prominent star, magnitude 2.50 Saik, Zeta Ophiuchi. Position your scope on
the star, insert a medium power eyepiece and scan slowly and carefully
south-southwest. This magnitude 8.85, 13.0’ across star cluster likely ain’t
gonna put your eye out, so be careful.

On the
cluster’s field, my 10-inch Dobsonian, Zelda, showed
this as a loose looking globular with but a few stars resolved. This was on a
typical hazy summer backyard night. Under better conditions, M107 will look
better, but as I noted in my long entry, “It’s a Messier, but truly not much of a Messier.”

M108: The Surfboard Galaxy

I’ve always
liked M108. It’s distinctive, and its nearness to another of my favorite
objects, M97, the Owl Nebula, adds even more interest. But we are a long way
from “spectacular” here. Under suburban skies, anyway. In an 8-inch telescope,
M108 is a dim streak, as its stats would suggest: magnitude 10.70 and a size of 8’42” x 2’12”.
In an 8-inch in my backyard, it is often an averted vision object. It is better
in the 10-inch (a 10-inch really gives you a leg up in the backyard), but not
worlds better.

Like M107,
M108 is at least trivial to find. If you can locate the Owl manually, all you
have to do is move the telescope 48’ west-northwest roughly back in the
direction of the bright dipper bowl star Merak. If you are coming from Merak,
move 1-degree 30’ northeast. As with M107, but even moreso, go slowly. Higher
magnification, maybe with a wide-field 12mm ocular, will help.

Don’t expect
too much when you do find this bugger. You should be able to tell it is
elongated, but that will likely be about it. From a better location than the
backyard, things do improve in a hurry. In an 8-inch at the club dark site, I
can begin to make out dark detail that makes the galaxy look somewhat like a
miniature M82. In reality, this object is nothing like weirdly disturbed M82,
being a more normal dusty spiral.

M109

M109

In a large
aperture scope, or with a deep sky video camera, Ursa Major’s M109 is
distinctive and interesting looking. It’s what I used to call a “tie-fighter
galaxy” when I was doing the Herschel Project. It’s a barred spiral that looks
a lot one of Star Wars’ bad guy spaceships if you’re seeing the bar without the
full extent of the delicate and dim spiral arms that extend from it. Other
people call these “theta galaxies,” but that’s other people, not me. At
magnitude 10.6, M109 is not overly bright, but neither is it too large at 7’36”
x 4’42”, so it is at least doable from average suburban digs.

Like M108,
M109 is easy to find thanks to its proximity to Phecda, the dipper bowl star.
Move 29’ south-southeast of the star and you should have M109 centered. With a
12mm wide-field, you may be able to move the star to one edge of your field and
have the galaxy visible on the other edge if your scope isn’t overly long in
focal length.

What you
will be able to make out of M109 depends on scope and sky. With 8-inch and
smaller instruments, all you are likely to see from the backyard is a dim oval
thing that may require averted vision. Even with larger aperture telescopes at considerably better sites, you still
may not pick up much beyond that. Well, perhaps a subdued nucleus. To see the bar
and arms, I cheated, using my Mallincam deep sky video camera on the C11, which
made the galaxy’s tie-fighter aspect easy from my back forty.

M110

And, finally,
at the very end of the road is one of M31’s two nearby satellite galaxies, a
magnitude 8.07 E5 elliptical. While it is rather bright, it’s also fairly large
(21’54” x 11’00”) and is not always trivial from the backyard. It is much more
difficult than M32, and on poorer nights M110 can be surprisingly difficult—or
invisible—with a 4-inch.

M110

At least you
don’t have to worry about hunting. Surely, you can find its great parent galaxy,
M31, if you are beyond the greenhorn stage. M110 is located 38’ northwest of that
huge beast (farther from the center than the brighter satellite, M32, that is).
It is well separated from the “nebulosity” of the galaxy.

On good
nights, M110 can be tantalizing, even from the backyard. In a 10-inch, I can
not only see that it is quite elongated, as befits it with its E5
classification, and that it brightens towards its center, but that there are occasionally
tantalizing hints of dusty detail just on the very edge of perception.

And that…is
all. I hope you’ve enjoyed the series, and I also hope that, if you haven’t
seriously attacked the list yet, I’ve encouraged you to do so. Folks, there is
an absolute lifetime of enjoyment in these special objects.

Nota Bene:
What do I use these days when I need a planetarium program? I use Stellarium. It does everything I need to do and
more. And it is free, and you know I like that.
The news is that version 15.1.1 is on the streets, and the program is better
than ever, now including a DSS function that allows you to superimpose DSS
images over the charts (if you have an Internet
connection). There is no reason not to upgrade, folks; go get it.

Sunday, January 01, 2017

Issue #524: Good Riddance 2016

Hello 2017! Just hope you are better than the monster of a year that’s
just departed. Bad as it’s been for numerous reasons, li’l old optimist
me at least takes comfort in—what else?—the eternal stars. Oh, they are not really
eternal, but they seem so for ephemeral creatures such as ourselves. I’ve
learned that when my path is dark and dim, those distant stars can illuminate
it. I am comforted to look up and see the stars of Orion look just as they
did when I was a boy.

Anyhoo, in lieu of the next Messier
column, which will come next week, I give you my yearly summary. Reading back
over all these articles, what was the main thread this past annum? If I had to sum up
my astronomical year in a few words? I guess it would be “the year of the
refractor.”

If you were reading the blog in 2015,
you probably noticed, maybe even with dismay, my gradual transition to refractors,
which was presaged by the beginning of a series of articles called “The Refractor Way.” If those
had paved the way, this one cemented things. This entry recounts the arrival of
my SkyWatcher Pro ED 120.

It was one heck of a big change. The
telescope I sold to finance the new refractor was my time-honored Dobsonian, Old
Betsy, who had been with me for over 20 years, the peak years of my amateur
astronomy career. Everything turned out OK, though. While I sometimes still miss
Betsy, I wasn’t using her, and her replacement, Hermione Granger, is good at so many
things, including visual observing, where she competes well with a C8. It was indeed
the beginning of a beautiful friendship.

You must have been living under a rock
if you haven’t been aware of how big an effect smartphones and tablets have had
on amateur astronomy. The astronomy apps we’ve got now, like SkySafari, are
incredibly powerful. At the time this article came out, I hadn’t yet tried
interfacing scope + phone, but even without that, the utility of smart devices
for our avocation was more than obvious. Last nail in the coffin of print star
atlases? Maybe.

The next two articles in my refractor
manifesto concerned a big dream of mine (regarding amateur
astronomy, anyway). I’d wanted that holy grail, the 6-inch refractor, since I
was too young to have even been able to lift one. I finally realized that dream
last January in a surprisingly inexpensive fashion.

It isn’t just telescopes where I
appreciate "simple and easy" these days. Stellarium, the free planetarium
program, is both those things, but it is also profoundly, powerful. In these latter days, there
are not too many astronomy things I want to do that I cannot do with
Stellarium.

As above, smart devices (and computers)
may have somewhat supplanted the print star atlas, but there are still good
ones, and some of us still like to use paper star maps at least part
of the time. There are even new print atlases being published, like Sky & Telescope’s Pocket Sky Atlas Jumbo
Edition. It won’t really fit in your pocket, but it is a substantial
improvement on its already great predecessor. Just get it, even if you have
SkySafari.

Namely, the AR102 achromatic refractor
from Explore Scientific. Yeah, its dew shield sure is funny looking, but you
get so much for your money. Great f/6.5 optics, a decent finder, an excellent
star diagonal, and maybe most of all, a kick-butt focuser. Everyone should have
one, and given its modest price almost everyone can. The legitimate heir to the
much-loved Short Tube 80 of the 1990s.

Occasionally I feel the need for the
SOMETHING DIFFERENT. This time that was Pensacon 2016, Pensacola, Florida’s big
comicon. Had a wonderful time, bought some cool stuff, and saw one of my idols,
Neal Adams.

“Big Ethel” being my new 6-inch
achromat. What did I discover? When collimated, she became a powerful
performer. Also, the Celestron VX mount was up to the task of holding this big tube.
Or would have been if I’d had a pier extension for the tripod. As it was, I had
to be careful not to let the tube bump into the tripod, which would happen when
slewing anywhere near the zenith.

This article, which formed the basis
for my recent Sky & Telescope
“Focal Point” column, concerns the battle over computerized
telescopes in astronomy. I actually think this war is over, since my column
didn’t create nearly as much controversy as my last Focal Point on buying stars
did (why do a Focal Point if you can’t ruffle some feathers with it?).

A lot of you sure have some weird
ideas about the astronomy magazines, and especially Sky & Telescope. What kind of weird ideas? I’ll direct you to
the Cloudy Nights “Astro Art, Books, and Websites” forum if you want a taste.
Herein, I try to correct some of those occasionally odd misconceptions.

Well, is one? While I primarily use
refractors these days, a lens scope wasn’t always the scope for me. While they noware the scope for me, that doesn't mean they are for you. The quiz at the end of this article should help you
decide if you are a refractorphile in the making.

This far in, with Messier 36 – 41, I
was finding out that, surprisingly, writing about these good old DSOs was not
boring at all. Not only was it fun, I found I still had a lot to say about them
(even after writing a book, The Urban
Astronomer’s Guide, which covered many of them in detail).

This (smaller, more informal)
springtime edition of our local star party was notable for several reasons. It
was my first experience imaging with Hermione Granger under truly dark skies,
the spring weather actually cooperated fully for once, and I only stayed two days. Lately, I find two – three days at a star party is quite enough, and was
happy to scurry home on Saturday to enjoy Free Comic Book Day.

This batch, which featured M50 – 56, found me, almost unbelievably, at the halfway point. Things would slow down a
bit for a while after this, however, since I spent much of the summer traveling to distant
star parties and astronomy clubs.

There are plenty of great deep sky
observing planning programs like SkyTools and Deepsky, but I make no bones here
that the one I’d used most in recent times was Phyllis Lang’s venerable
Deep Sky Planner. “Venerable,” sure, but Ms. Lang had just updated her soft
with version 7 and guess what? It was better than ever.

We all—well most of us anyway—love the
Messier objects. The question on my mind, however, and perhaps on those of my
fellow increasingly lazy baby boomers, was “How small a scope can you use to
profitably view the list?” In the process of writing this one, I had a ball observing
the Ms in the backyard with 4-inch and 3-inch telescopes.

It was, as July ran out, time to get on the road for the late summer and early fall star party season. The first
stop was a week at the Maine Astronomy Retreat way up north. To sum up: great observing, great people, great food,
great facility. I’d go back anytime. Only slight bummer? Had nothing to do
with the retreat, but with my airline. My flight out of Boston was cancelled.
I spent an evening in a hotel in the midst of an industrial park near Logan.
Oh, well…the hotel bar and cable TV kept me entertained. And it was nice to
enjoy the air conditioning after an uncharacteristically warm week in Maine.

Next stop was the NWSF in a state I’d
never visited, Wisconsin. This was another great time. A little shorter, but
great food, people, and observing too. Nice facility, and to top it all off,
tenderfoot me “camped out” in a brand new Fairfield Inn and Suites. Coming back
to that beautiful new room each night helped make a great experience even
better.

I’ve been to this star party, held in
West Virginia on the slopes of Spruce Knob Mountain, so many times over the
last decade that it was difficult to find something new to write about.
Nevertheless, great skies and friendly folks made this a winner. For me, “no
surprises” is a good thing.

I observed the 2500 Herschel objects
over the course of about three years. I don’t consider that a huge feat; it was
more just having the right equipment, a plan, and a little perseverance. People
still ask questions about how I did it, though. While this article did answer
some of those questions, its main goal was to encourage you to get out and
begin the Herschel 400. Come on in the water is deep but fine.

Though I was close to the end of my
main Messier series, having nearly covered ‘em all, I still thought it would be
a good idea to give short “executive summaries” on all the objects in two
articles, since the fall observing season was upon us and many folks would be
out in the old backyard chasing Ms.

After those go-go years of the
Herschel Project, it’s nice to spend a star party doing leisurely visual
observing. Which is exactly what I did at the 2016 DSSG using my 6-inch
Achromat. She performed beautifully (people were sure she was an ED scope). As
is my wont of late, I was only on-site for three nights of the 5-night event,
but those were the best nights of the star party. Sometimes I do get lucky.

What do the experts say? You can’t do
astrophotography with a fast achromatic refractor. I set out to see if that was
true. Was it? Read the article to find out, but I will say the humble Explore
Scientific AR102 is one heck of a little jack of all trades.

Didn’t want to be a Debbie Downer, but
a couple of years of philosophical musings about my life led to some musings
about amateur astronomy and its fate as well. The answers I arrived at may, alas, not
make you happy. This article garnered the most attention and responses of any
in 2015. Don’t wanna toot my own horn overmuch, but this is a must-read,
campers.

And, so, with my traditional Christmas
Eve message to my readers, we were done for another year. What will 2017 hold?
My crystal ball is hazy on that, folks. Let us hope for the best, however, and
keep fingers and toes crossed. OH, I think it will be a great year for
astronomy no matter how the eclipse goes weather and crowd-wise. The rest,
though? I am not so sure about that, I must admit.

Nota Bene:
As I’ve mentioned, Steve Tuma is discontinuing sales and support of his
excellent Deepsky program. Steve tells me he’s looking for a server somewhere
to upload the program files to so everybody can continue to download and enjoy
the program—for free. If you know of a suitable site, please contact Steve at
stuma@comcast.net